The move meets a demand by Afghan President Hamid Karzai that US forces withdraw from the area after allegations that their Afghan counterparts committed human rights abuses there.

Major General Tony Thomas, who is the top US special operations commander in Afghanistan, told the Associated Press that Afghan special forces have taken the Americans' place and will work alongside local Afghan policemen to stop insurgents using the area to attack the capital, Kabul.

Maj Gen Thomas said US commandos will continue to operate throughout the rest of Wardak province.

Attaullah Khogyani, spokesman for the governor of Wardak province, confirmed that US special operations forces had withdrawn and been replaced by a joint Afghan security forces team.

The transfer of authority ends a controversial chapter in which Mr Karzai accused US troops and an interpreter working with them of torture, kidnapping and summary execution of militant suspects in Nirkh - charges that US officials, including top commander in Afghanistan General Joseph Dunford, firmly denied.

The incident shows the larger struggle of Mr Karzai's government to assert its authority over security matters, even as its green security forces try to assume control of much of the country from coalition forces on a rushed timeline, ahead of the scheduled withdrawal of most of coalition forces by December 2014.

Mr Karzai had originally demanded that US special operations forces pull out from the entire province, a gateway and staging area for the Taliban and other militants for attacks on the capital Kabul. But he scaled down his demands to just the single district after negotiations with Gen Dunford and other US officials.

"President Karzai was specific, it's only for Nirkh, that was a provocative point," Maj Gen Thomas said. "American special operations forces are integral in the defence of Wardak from now until the foreseeable future."